Needle guides may be used to assist in positioning and guidance of needles in a variety of applications such as biopsies, fluid aspirations, and regional anesthesia procedures. In some examples, needle guides may be used together with ultrasound probes in order to guide a needle to a particular position in a patient's tissue. For example, a needle guide may be attached to an ultrasound device to guide a needle during regional anesthesia procedures.
The accuracy, precision, and measurement resolution of needle placement when using needle guides is of importance to the clinician. While some anatomic targets, such as the internal jugular vein, are relatively large and therefore will tolerate guides that lack accuracy, precision, or resolution, procedures that target small structures or are near sensitive tissue are less forgiving.
For most in-plane ultrasound needle guides, the needle can be visualized throughout its trajectory to the target, and the clinician may dynamically correct for any shortcomings in the needle guide, or may choose to not use any needle guide at all. However, for out-of-plane ultrasound needle guide approaches, the needle is not visible until it intersects the plane of the ultrasound image, making needle guides much more useful and the characteristics of the needle guide more important. Additionally, in some in-plane approaches, steep needle trajectories make needle visualization difficult.
Some anesthetic procedures, e.g., paravertebral blocks and lumbar plexus blocks, may be difficult to perform using in-plane ultrasound needle guide techniques due to the desired needle depth, presence of anatomical obstructions, the size/geometry of the ultrasound probe and the altered needle trajectory created, and the steep angle of needle entry, for example. Nevertheless, such anesthetic procedures could benefit from ultrasound guidance.
Some needle guide approaches have changed the selected depth by changing the angle at which the needle penetrates the skin, in a variable-angle style needle guide. However, such needle guides have a limited number of depths and angles available, making them unsuitable for the fine degree of control needed for regional anesthesia. Furthermore, such approaches may not provide any safety mechanism that limits the advancement of the needle, e.g., to reduce inadvertent puncture of vital structures. Further, some approaches provide single use guides which employ differently-shaped clips to achieve different depths, thereby potentially creating confusion during use when selecting the appropriate clip for a desired depth. Because of these issues, many practitioners either do not use an ultrasound probe or ‘free-hand’ the needle for these procedures. Further, since such approaches are considered to be relatively difficult procedures, they may be performed with less frequency relative to the number of surgeries where patients could obtain benefit from these blocks.